The present invention relates generally to sealed system testing equipment and, in particular, to a self-contained portable air pressure decay test apparatus.
Hydraulic systems, such as automotive vehicle brake systems, are well known. These brake systems may be tested in the assembly plant prior to delivery of the vehicle to ensure high quality operation. Brake systems are typically tested by utilizing a prior art testing device, or tester, that applies a predetermined force to the brake pedal or brake master cylinder. As the force is applied to the pedal or brake master cylinder, the distance that the pedal or cylinder travels over a predetermined length of time is measured. The distance traveled by the brake pedal versus time is compared to a predetermined value to assess the hydraulic integrity of the brake system. In addition, hydraulic system variations are such that they can result in prior art testing devices giving indications of a false negative result or a failed test even though there is no traceable sign of a leak.
Prior art testing devices, however, are typically mounted to a processing monument or a similar fixed point on an assembly line and are connected to the processing monument with hoses and electrical cables. Because the hoses and electrical cables essentially tether the testing device to the assembly line, the testing device disadvantageously has very limited mobility. This limits the assembly plant flexibility because the brake system can only be tested when the vehicle is adjacent the processing monument. Furthermore, the device is expensive to manufacture. In addition, the prior art testing apparatuses may cause occasional paint mutilations on the vehicle surface when the hoses and the electrical cables inadvertently contact the vehicle surface. The prior art testing device also increases assembly plant operations costs as a result of their required maintenance and is an operator ergonomic issue because of its mass, including the hoses and electrical cables attached thereto.
It is desirable, therefore, to provide an apparatus for testing hydraulc systems, such as an automotive vehicle brake system, that is portable and self-contained for easy and flexible use in an assembly plant operation.
The present invention concerns a portable air pressure decay test apparatus for leak testing of a sealed system. The apparatus includes a hollow housing, an air pump and associated valves and pressure measuring devices having an inlet and an outlet disposed in the housing, and a controller disposed in the housing and connected to the pump for controlling the operation of the pump, valves and pressure measuring device. A test head is mounted on the housing for releasably attaching to an access or attachment point of a sealed system. The test head is in fluid communication with the outlet of the pump. When the test head is attached to the attachment point of the hydraulic system, the controller operates the pump to provide pressured air to the sealed system and raise the pressure in the sealed system to a predetermined value. After the predetermined value of pressure is reached, the controller stops the pump, isolates the system and monitors the air pressure in the sealed system for a predetermined time interval to measure an air pressure decay rate. The controller then compares the measured air pressure decay rate with a predetermined air pressure decay rate to indicate if a leak rate of the sealed system is acceptable. The apparatus preferably includes a power source connected to the pump and the controller disposed in the housing. The power source is preferably a removable battery, a rechargeable battery, or the like.
Preferably, the hydraulic system is an automotive braking system and the attachment point to the braking system is the fill tube or opening of the master cylinder hydraulic fluid reservoir. The apparatus preferably includes an adapter foot attached to the housing that is adapted to clamp on to a threaded portion of the fill tube prior to testing the braking system. Preferably, the test head is connected to the outlet of the pump by an elongated pipe or rod. An actuator lever is attached at an upper portion of the housing and is operable to actuate the rod and test head and extend the rod and attached test head into the master cylinder hydraulic reservoir. An on/off switch is connected to the power source and the pump and is operable to start the pump when actuated. A plurality of pneumatic valves is disposed intermediate the outlet of the pump and the rod and test head. A pressure measuring device such as a transducer is pneumatically linked to the system through the test head and is operable to sense the pressure of the hydraulic system when a test cycle begins.
The portable air pressure decay unit is a fully self-contained ergonomically designed tool running on removable or rechargeable batteries. The benefits of the portable air pressure decay apparatus include, but are not limited to, lower tooling cost because the present invention is much cheaper to produce than the expensive prior art testing device. The present invention will also produce fewer variation related false negative test results and thus yield higher first time pass rates. The present invention also provides the ability to easily move the brake test operations within the assembly plant in order to balance the assembly line better and increase the assembly line efficiency. The present invention eliminates a processing monument in the assembly line, which increases the assembly plant flexibility. The present invention also eliminates potential paint mutilations caused by inadvertent contact of the air hoses and the electrical cables with the vehicle surface because the present invention advantageously does not require the external air hoses and electrical cables of the prior art testing device. The present invention also lowers assembly plant operations cost by reducing maintenance requirements because the present invention is much cheaper to produce than the prior art testing device. The present invention also provides improved operator ergonomics through the elimination of the mass of the prior art testing device as well as the bulky hoses and electrical cords.